- What is Adrenaline? -
Adrenaline is a software that modifies the official PSP Emulator using taiHEN CFW framework
to make it run a PSP 6.61 custom firmware. Thanks to the power of taiHEN, Adrenaline can
inject custom code into the IPL which allows unsigned code to run at boottime.

Which pretty clearly explains that PSVita has a low level emulator running actual firmware and that adrenaline modifies it to run different firmware.
PPSSPP on the other hand is high level and from the very design doesn't deal with any firmware at all and never will be.
If you want a low level PSP emulator that could run your favourite firmware with it's outdated XMB ui, better create a completely new emu from zero. And if all you want is XMB looks, go hunt for some frontends/launchers which allow enough customization to simulate whatever looks you want.

- What is Adrenaline? -
Adrenaline is a software that modifies the official PSP Emulator using taiHEN CFW framework
to make it run a PSP 6.61 custom firmware. Thanks to the power of taiHEN, Adrenaline can
inject custom code into the IPL which allows unsigned code to run at boottime.

Which pretty clearly explains that PSVita has a low level emulator running actual firmware and that adrenaline modifies it to run different firmware.
PPSSPP on the other hand is high level and from the very design doesn't deal with any firmware at all and never will be.
If you want a low level PSP emulator that could run your favourite firmware with it's outdated XMB ui, better create a completely new emu from zero. And if all you want is XMB looks, go hunt for some frontends/launchers which allow enough customization to simulate whatever looks you want.

It emulates a gasoline powered car, and has the same problems with potholes on the roads that a gas car would have. But, even if someone releases really amazing spark plugs, or some new amazing kind of oil... it doesn't really help PPSSPP. Even though PPSSPP can still drive on roads, the engine inside it is totally different from the engine in an old gas car.

Unlike roads (games), CFW and the XMB hook directly into the gas and the oil. They just don't work in an electric car, they have to be rebuilt for electric and that's life.